Nitrogen, which is vital for plant growth, is present in animal excreta and synthetic fertilisers that are applied to land to boost crop production. But excessive and inefficient use of this nutrient means up to 80% of it leaks into the environment, mostly in various polluting forms of nitrogen: ammonia and nitrogen oxides, which are harmful air pollutants; nitrous oxide, a potent greenhouse gas; and nitrate, which affects water quality.
A new report coordinated by the UK Centre for Ecology on behalf of the Task Force on Reactive Nitrogen under the UNECE Convention on Long-range Transboundary Air Pollution has put forward solutions to halve nitrogen pollution from agriculture and the food system in Europe, including reducing meat and dairy consumption, fertiliser use and food waste.
The Appetite for Change report says inefficiencies in farms, retail and wastewater practices mean that the nitrogen use efficiency of the food system in Europe is only 18%, leaving most of the remainder leaking into air, water and soils.
The report puts forward a recipe to halve these overall losses, and its 'ingredients' include:
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Halving average European meat and dairy consumption, replaced by more plant-based diets, which would cut pollution and improve human health;
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More efficient fertiliser application and storage of manure;
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Cutting food waste by retailers and consumers, so reducing the amount that needs to be produced;
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Better wastewater treatment to capture nitrogen from sewage, which would reduce emissions and enable recycled nutrients to be used on fields;
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Help the shift towards more balanced diets by providing financial incentives for foods that have a low impact on the environment and adopting public sector catering contracts that offer these sustainable food choices, for example;
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A coherent combination of policies addressing food production and consumption to better support a transition towards sustainable systems;
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Farmers, industry, government and consumers need to be mobilised and agree to work together to reduce nitrogen losses throughout the food system, for example through setting up governance platforms at national, regional and local levels.
Professor Mark Sutton of UKCEH, co-chair of the Task Force on Reactive Nitrogen and one of the editors of Appetite for Change, explains: "Action does not begin and end at the farm gate; it requires a holistic approach involving not only farmers but policymakers, retailers, water companies and individuals. It is also not saying we should all become vegan. Our analysis finds that a broad package of actions including a demitarian approach (halving meat and dairy consumption) scored most highly in looking to halve nitrogen waste by 2030."
The report uses the ambition to half nitrogen waste by 2030 as a focus since this has been set by the UN Colombo Declaration and extended by the Kunming-Montreal Global Biodiversity Framework.
The protein consumption of the average person in Europe greatly exceeds recommendations of the World Health Organization. The report says a balanced diet that has less meat and dairy would improve nutrition and make people healthier, reducing demand on health services.
Appetite for Change builds upon the Nitrogen on the Table report in 2014, which set out the problem, saying the food system in Europe, especially livestock, accounts for 80% of the continent's nitrogen emissions.
In addition to reduced emissions compared to livestock agriculture, growing vegetables and other plant produce is typically more efficient than livestock agriculture, requiring less land and fertilisers.
Some 40% of farmland in Europe produces food for livestock, though there is also heavy dependence on imports of feed, such as oil seeds and fertilisers. Nitrogen fertiliser costs for farmers have spiked in the past two years, largely as a result of the war in Ukraine, emphasising the need to reduce the wasteful losses of expensive nitrogen resources.
Dr Adrian Leip, an environmental scientist at the European Commission, who is lead editor of the report, commented: "The unprecedented rise of energy, fertiliser and food prices since 2021 underlines the need to address the vulnerability of the current food system. Plant-based diets require less land and fertilisers, reduce energy use and increase our resilience to the current multi-crises: food, energy, climate. Freeing up land to restore habitats would help tackle the climate and biodiversity crises."
For Appetite for Change, the scientists investigated 144 scenarios, involving varying reductions in meat and dairy consumption, agricultural and retail practices, and investment in wastewater treatment. They looked at the benefits or trade-offs for the environment and health, severity and costs of possible measures.
Considering all the scenarios, the researchers concluded a balanced range of actions, including halved meat and dairy consumption ('demitarian' approach) with improved farm and food chain management could achieve a 49% reduction in nitrogen losses, and had the highest score for net societal benefit.
Of the many scenarios explored, the report found that a plant-based diet combined with ambitious technical measures could reduce nitrogen waste by 84%; this scenario did not offer net societal benefit when the environmental benefits were offset against the stringency of actions needed to achieve this.
The Appetite for Change report was produced by a group of researchers coordinated by the UK Centre for Ecology & Hydrology (UKCEH), the European Commission, Copenhagen Business School and the National Institute for Public Health and the Environment (RIVM) of The Netherlands.
The report is available on the taskforce's website.
Notes
Explanation of the societal benefit score
A social benefit score was calculated for each of the options combining different ambition levels for nitrogen reduction at farm level or in the food chain, reduced excess consumption of energy or protein, or switching to more plant-based diets. An initial score was attributed to each option, representing its contribution to the implementation cost of technical measures, the health or ecosystem benefits, or the socio-cultural barrier for stringent measures. The scores for these four effects were combined to an overall social benefit score applying equal weights.
About nitrogen
Unreactive nitrogen (N2) forms 78% of the Earth's atmosphere and is benign. However, reactive nitrogen can be a harmful pollutant. There are various forms, including:
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Ammonia gas (NH3), produced by livestock and fertilised fields, which causes biodiversity loss and combines with other gases such as nitrogen oxides to produce fine particulate matter (PM2.5) in the atmosphere which can aggravate respiratory and heart conditions, leading to millions of premature deaths.
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Nitrogen oxides (NOx) which mainly comes from combustion in transport and industry, but is also emitted from fertilised fields.
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Nitrous oxide (N2O), a greenhouse gas that is 300 times more potent than carbon dioxide. contributes to global warming and depletes the ozone layer.
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Nitrate (NO3-) from chemical fertilisers, manure and industry pollutes rivers and seas, posing a health risk for humans, fish, coral and plant life.
About the UNECE Convention on Long-range Transboundary Air Pollution
The UNECE Convention on Long-range Transboundary Air Pollution was adopted in 1979. Over the years, it has been extended by eight protocols that identify specific measures to be taken by Parties to cut their emissions of air pollutants, such as nitrogen oxides (NOx) and ammonia (NH3). The Convention has 51 Parties, covering North America and almost the entire European continent.
